Leaves curling, burned tips- Coco (healp)

[Waira]

..huh, definitely some progression there,... tips look worse, interveinal chlorosis is more marked,... weird as hell to see that up so high, as Mg is readily mobile within the plant,.. So, you feeds are at about 600ppm, but the r-o is as above? If so, then for sure you have serious nute salt build-up happening,... This can lead to uptake issues, Mg for sure... So, if I have it right on your input/r-o ppm's, then it's flush time, and maybe lay off the CO2 for a bit while this gets stabilized,.. from what I've been recommended, a flush in coco needs be done differently than true soil: RO/Di water, with 150ppm Ca-Mg (low N preferred), plus 150ppm appropriate nutes (for the plants stage), pH to 6.0,.. this will reset the CEC on the coco and purge the excess out,... pour through until your inputs ppm are at or close to r-o ppm's,...
...I can't advise at all on the CO2 mate, I'm mainly a Sun and soil grower,.... I have heard unconfirmed (scientifically) info about such margin curling with Mg defc., but never got a solid confirmation on that,... but it's certainly possible with the CO2 and photon-bomb lights, a nutritional deal is now the limiting factor, and in such circumstances, may be that symptoms don't manifest in the usual way,...